1. Field of the Invention
This specification relates to a digital electric power meter or a smart meter, and more particularly, to an electric power meter capable of monitoring a contact status of a latch relay mounted to a digital electric power meter or a smart meter, the latch relay capable of opening or closing at least one of power supply lines connected from an electric power source to an electric load.
2. Background of the Invention
The conventional digital electric power meter having a function to open and close power supply lines connected to a load side may be referred by the patent document registered by the present applicant (Patent Document 1: KR10-1017761 B1).
In the conventional digital electric power meter disclosed in the aforementioned patent document, even if a controller of the digital electric power meter has output a command signal for opening or closing a contact of a latch relay which opens or closes electric power lines, to the latch relay, the contact of the latch relay may not be open or closed in response to the command signal, due to failure of the latch relay, inferiority of a control power supplied to the latch relay, etc. In this case, since an open or closed status of the latch relay is determined based on the control signal of the controller, an open or closed status different from the current actual open or closed status may be displayed on a display unit of the digital electric power meter. That is, a power supply status or a power interruption status different from the actual power supply status or power interruption status may be erroneously displayed on the display unit.